New parenting: When, and to what, will my baby change eye color?

A baby’s eyes darken as the get older, and they might change color entirely. What color will your child’s eyes be?
Most questions about a baby are answered as soon as it is born, if not sooner. Boy or girl? A head of hair or completely bald? Does he have all five fingers and toes?

Eye color is one of the few things that isn’t settled by birth. Most babies are born with light eyes. This is because their eyes haven’t fully finished developing. A substance called melanin, the same chemical that determines the color of your skin, also determines the color of your eyes.

How long before we know for sure?
Exposure to light is what darkens eyes, similar to the way skin tans when exposed to sunlight. As your baby ages through her first year of life you will see her eye color gradually begin to darken. This process will finish somewhere around six to nine months, although some children might not have their eye color settle down until after their first year.

New parenting: When, and to what, will my baby change eye color?

It sometimes happens that a blue-eyed child will have his eyes turn green, usually around two or three years old. There have also been cases in which an adult’s eyes have changed color for no discernable reason. These sort of cases, though, are very rare.

The science of eye color

Exactly what color your baby’s eyes will be is a far more complicated matter. For years the assumption was that eye color followed the rules of Mendelian heredity; brown was dominant and blue was recessive. While two brown-eyed parents could have a blue-eyed baby, it was believed two blue-eyed parents could never have a brown-eyed baby.

Scientists now know that isn’t true. It is indeed possible for blue-eyed parents to have a brown-eyed baby, though it’s rare and not fully understood.

The melanin in your eye comes in two types: eumelanin, a dark brown pigment, and pheomelanin, a reddish yellow pigment. It is how they are proportioned in your iris (the colored part of your eye) that determines your exact eye color. Those proportions are determined by your genes.

Three genes have been discovered that control eye color. One gene selects for blue or green, a second selects for blue or brown, and the third always selects for brown. Geneticists don’t yet understand exactly how these interact, though, or what causes other eye colors. There might be genes for other colors, or it could be that other genes, while not directly controlling eye color, influence those genes that do directly control color.

So what color will my baby’s eyes be, already?

If you want to try to guess your baby’s eyes color, the best way is to look at your extended family. Draw up a chart listing the eye colors of grandparents, aunts and uncles. Include great-grandparents if you know what color their eyes were.

Analyze the patterns you see. Is one color more common than another? Are lighter colors like blue and green more typical in your family than brown? Or does everyone have hazel eyes?

Pay attention to skin tone, too. Darker skinned people (who have more melanin in their skin and eyes) tend to have darker eyes; lighter skinned people tend to have lighter eyes.

While your baby’s eyes are most likely to look like everyone else in the family, don’t be surprised if you wind up with something completely unexpected. If blue-eyed parents can have a brown-eyed baby, who knows what color you might see some day in your baby’s eyes?

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